As an example of a power semiconductor device, an insulated gate bipolar transistor (IGBT) has been known. In the IGBT, a method of suppressing discharging of holes from an n-type drift layer has been used to decrease on-resistance between a collector electrode and an emitter electrode. In this method, the holes discharged from the n-type drift layer to the emitter electrode are suppressed, so that an injection amount of electrons is relatively increased, thereby decreasing the on-resistance of the IGBT. For example, a structure in which p-type layers (dummy regions) interposed by trench gate electrodes between p-type base layers and electrically insulated from each other are provided, so-called a trench injection enhanced gate transistor (IEGT) has been suggested.
In the trench IEGT, excessive holes accumulated in the dummy region are discharged at the time of turning-off. However, efficient hole discharge may be disabled in an end of an device region (or an active region). In this case, a current may be concentrated at the end of the device region, the enormous current may flow, and a device may be braked down.